Memory: SRAM and DRAM

SIMM30

8/9-bit 30-pin Single Inline Memory Module.
If present, the parity (DP8) bit has separate data I/O and /CAS signals.
At one time, SIMMs with soldered-on pins (called SIPs) were also available.
Note: A11 is used as a battery connection in the DS2219 nonvolatile DRAM.

SIMM72

32/36-bit 72-pin Single Inline Memory Module.
The DPn bits are the parity bits and aren't present on 32-bit SIMMs.
'Odd' size SIMMs (512k, 2M, etc) have two banks, with RAS0/2 addressing
the primary, and RAS1/3 the secondary bank. RAS0/1 address the lower
18 bits (D0-17) and RAS2/3 the upper 18 bits (D18-35), while the CAS
lines can be used as byte-select. The four PD bits are the presence
and size-detect outputs.

DS1285, DS1287, DS1287A

Real-time clock with 50 bytes RAM.
DS1287(A) has built-in quartz crystal and lihium battery, and therefore
the X1, X2 and VBAT pins are no-connect. On the (older) DS1287 the /RCLR
pin is no-connect as well.